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Albumen print: A type of photograph invented by Louis Desire Blanquart-Evrard of France in 1850 and in use through the early 20th century. An albumen print was produced on a thin piece of paper that was coated with albumen (egg whites) and salt, floated in silver nitrate, and then mounted on cardboard. Ambrotype: A type of photograph patented in 1854, in which the pictures were produced on glass instead of a metal plate. Some considered them an inexpensive improvement over daguerreotypes because of the less reflective quality, but they lacked detail and tonal range.Autochrome: A photographic plate patented in 1904 by Auguste and Louis Lumiere. In 1907 they began to commercially market the process, which used microscopic red-, green-, and blue-violet-dyed grains of potato starch mixed evenly and coated onto a sheet of glass. During exposure, a black-and-white emulsion flowed over this layer and caused the grains of potato starch on each plate to act as millions of tiny filters. The light-sensitive emulsion was then reverse-processed into a positive transparency that filtered the light passed through the emulsion to display the proper color of the starch grains, creating a mosaic of glowing dots on glass similar to the look of a pointillist painting. Carbon print: A process patented by Joseph Wilson Swan in 1864 that offered a permanent print without grain, with a wide tonal range. Negatives were printed onto a tissue containing carbon and other pigments in a gelatin base made light sensitive by a bath of potassium bichromate. After processing, the image on the tissue could be transferred to a paper base and the backing of the tissue removed. Collodion print: A photographic process similar to that used for ambrotypes that created a matte, glossy, or semigloss albumen-type print. Although these prints lack the yellowish cast found in the whites of albumen prints, they are difficult to distinguish from other 1890 -- 1910 silver prints and usually must be validated by a trained conservator.Carte de visite: A type of photograph patented by photographer Andre Adolphe Disderi in 1854. It was a 2 1/2- X 4-inch-format paper print mounted on a card; collections were often bound together in photo albums.Cyanotype: A process invented by Sir John Herschel in 1842 that created brilliant blue images with a matte surface. It was most popular around the turn of the 20th century. Cyanotypes are highly stable because the process used iron salts (rather than silver compounds) for the light-sensitive material; the same process was used to make architectural blueprints.Daguerreotype: The first practical (albeit volatile, due to the lengthy exposure time required) form of photography, made public in August 1839. Daguerreotypes were made directly in the camera, not from a negative. The resulting “print ” was always displayed behind glass, in a frame or a small folding case. The American Museum of Photography Web site maintains an online display of examples, as well as a detailed history of this process . Dilute albumen print: An early variation of albumen print, with finer detail and tonality. Sometimes referred to as lightly albumenized print.

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